[TowerTalk] Request for Advice - Rohn 25 vs TRI-EX HZN 471
garyk9gs at wi.rr.com
Sat Feb 18 17:58:11 PST 2012
Seems like an awful lot of trouble when you can just buy an extra
section or two of used Rohn 25.
On 2/18/2012 6:33 PM, Bruce Ward wrote:
> You make a very sane suggestion.
> My reason for putting the tower on top of the building, if I do, is to
> get an extra 8' to 10' of height. The building will be sufficient to
> handle the 1100 pound weight plus the horizontal wind loads.
> The tower site is covered in 60' plus trees and there is a similar
> height hill with similar height trees between my tower and the far end.
> I need to get above the trees plus above the fresnel zone so I want to
> go as high as I can.
> If I use the Rohn 25G we will add sections until we are high enough.
> This method could mean that I have to build sufficient structure to
> bracket even higher than 35'. I would place the bottom section Rohn 25G
> on the ground (a concrete base) and bracket it to a pole embedded into
> the building.
> If I use the the TRI-EX I am stuck with its 70' height plus a 10' mast.
> Since it is a one shot deal I would like to start as high as I can.
> Thank you.
> On 02/18/2012 06:19 PM, Mark Robinson wrote:
>> I am not a mechanical engineer but why don't you put the tower in the ground
>> and the building next to the tower.
>> Mark N1UK
>> ----- Original Message -----
>> From: "Bruce Ward"<Bruce at IPIntel.com>
>> To:<towertalk at contesting.com>
>> Sent: Saturday, 18 February, 2012 6:53 PM
>> Subject: [TowerTalk] Request for Advice - Rohn 25 vs TRI-EX HZN 471
>>> I am setting up a tower (my first) to get internet service. The
>>> antennas will be less than 2 square feet of wind loading combined and
>>> could be even less using 2 11x14" grid antennas.
>>> My plan is to build a 10'x10' 9' to 10' tall block building on a slab
>>> that is larger in all directions. This building will will have a
>>> concrete roof with rebar and wire in all concrete. The blocks will have
>>> rebar and concrete in every cell. The structure will use 12 to 15
>>> yards of concrete plus 400 concrete blocks providing an over 45,000
>>> pound base for the tower. I have a civil engineer friend who will be
>>> involved in the final design of the building. The building is dual
>>> purpose, it will provide a secure home for my servers and a stable base
>>> for the tower.
>>> Now for the difficult part, I do not have room for guy wires.
>>> I am trying to decide between two options
>>> 1. I have 9 full and a top section of Rohn 25G in my yard waiting to be
>>> be installed. Currently Rohn rates the 25G for freestanding use up to
>>> 40' with 1.4 square feet of wind loading. From reading online it sounds
>>> like Rohn 25s have been used for decades even higher without guy wires.
>>> I do not want to risk stretching beyond Rohns specifications. I have
>>> access to 40' lengths of 8" pipe. If I go with the Rohn 25G my intention
>>> would be to embed a 40' section of the 8" pipe into the building and
>>> bracket to that pipe up to 35' or so then have the tower extend another
>>> 35' to 40' above the pipe. All the metal would be isolated from the
>>> ground and properly guided with a ground rod to avoid corrosion issues.
>>> 2. There is a TRI-EX HZN 471 available locally. I would have jumped on
>>> this one earlier but it is worth more the the current owner than it is
>>> to me. This is a 70' (71'?) crank up tower with a motorized winch. The
>>> motor is broken and would need to be replaced. The tower is free
>>> standing with the exception of three diagonal pipe braces that connect
>>> from the top of the bottom of the 4 sections to the ground around 10'
>>> out. I like that this tower is freestanding and I believe I could do
>>> away with the braces if I bracketed the tower at the same location to a
>>> sufficiently strong structure. If I used this tower I would likely
>>> build a 3'x3' column of solid concrete into my building and place the
>>> tower on top.
>>> I would very much appreciate any suggestions and advice.
>>> Thank you.
>>> TowerTalk mailing list
>>> TowerTalk at contesting.com
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